A known electrophotographic image forming apparatus includes a photosensitive drum and a developing roller. Along with the rotation of the photosensitive drum, an electrostatic latent image is formed on a peripheral surface of the photosensitive drum, and toner is supplied from the developing roller to the surface of the photosensitive drum.
This develops the electrostatic latent image to a toner image, and the toner image is carried on the surface of the photosensitive drum. The toner image is transferred from the surface of the photosensitive drum to a recording medium, e.g. a recording sheet, thereby the toner image is formed or printed on the recording medium.
In such an image forming apparatus, toner may remain on the photosensitive drum after toner image has been transferred to the recording sheet, and fixedly adhere to the surface of the photosensitive drum. This is a phenomenon called toner filming. Especially in a structure where the surface of the developing roller contacts the surface of the photosensitive drum, toner filming is likely to occur because toner carried on the surface of the developing roller slides on photosensitive drum. Toner filming may result in deterioration of image quality and short lifetime of the photosensitive drum.